1. Field of the Invention
The present invention relates to a seatbelt device of a vehicle. The seatbelt device ties down a passenger sitting on a seat of a vehicle by using a webbing.
2. Description of the Related Art
In recent years, a seatbelt device has been developed such that a motor pulls in a webbing based on need, and a passenger is tied down appropriately according to a condition of the vehicle (see, for example, Published Japanese Translation No. 2009-500236 of the PCT International Publication).
Incidentally, when a vehicle turns a corner or a sharp curve at a high speed, the upper body of a passenger seated on a seat may be jolted left and right as well as back and forth due to the acceleration. Currently, it is suggested that the swinging of the upper body of the passenger under such conditions be mitigated by using a seatbelt device.
In this case, the acceleration acting on the vehicle may be detected by a sensor, and a webbing may be wrapped up according to the detected acceleration. However, for example, when a predetermined amount of the webbing is wrapped up by the motor when the acceleration acting on the vehicle has exceeded a threshold, and the threshold is set to a small value, the webbing may tie down the passenger frequently. As a result, the comfort level of the passenger may be undermined. On the other hand, when the threshold is set to a large value, the webbing might not tie down the passenger when, for instance, the vehicle is in a turning motion.
Considering the problems described above, an object of the present invention is to provide a seatbelt device of a vehicle which appropriately determines the situation in which the passenger is required to be tied down, and enhances the efficiency with which the passenger is tied down, without impairing the comfort level experienced by the passenger.